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Perchlorate Reductase Is Distinguished by Active Site Aromatic Gate Residues
Matthew D Youngblut1, Chi-Lin Tsai2, Iain C Clark1
1From the Energy Biosciences Institute and.
The Journal of Biological Chemistry
|March 5, 2016
Summary
Perchlorate reductase (PcrAB) enzyme structure and function were elucidated. Key residues gate substrate entry and product release, revealing the mechanism of microbial perchlorate respiration.
Area of Science:
- Biochemistry
- Structural Biology
- Astrobiology
Background:
- Perchlorate is an essential ion for life on Earth and Mars.
- Perchlorate reductase (PcrAB) is crucial for microbial perchlorate respiration but its mechanism is poorly understood.
Purpose of the Study:
- To characterize the biophysics, phylogeny, and crystal structure of PcrAB.
- To elucidate the mechanism of biological perchlorate reduction.
Main Methods:
- X-ray crystallography (1.86-Å resolution) of the PcrAB complex.
- Biochemical analyses of enzyme kinetics and substrate inhibition.
- Structural analysis of oxidized and reduced PcrAB with substrate analog.
Main Results:
- PcrAB exhibits high perchlorate affinity (Km = 6 μm) and substrate inhibition, unlike nitrate reductase.
- Key residues in a funnel-shaped tunnel gate substrate access and product release.
- Specific Phe and Asp residues modulate tunnel conformation and active site coordination.
Conclusions:
- The study provides the first detailed structural insights into PcrAB mechanism.
- Identified gating residues are crucial for substrate entrance and product release.
- This work illuminates a critical step in the Earth's chlorine redox cycle.
Keywords:
DMSO reductase superfamilyMo-bis-MGDenzyme mechanismiron-sulfur proteinmolybdenumperchlorate reductasestructure-functionsubstrate access tunnelsubstrate inhibitionx-ray crystallographyMore Related Videos
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